1. Field of the Invention
The present invention relates to supercritical fluid chromatography (SFC) that uses a supercritical fluid as a mobile phase.
2. Description of the Related Art
In recent years, along with technological innovations such as sensitivity improvement in mass spectrometers and other such detectors, along with improvement in selectivity of molecules at the time of detection, exhaustive quantitative analysis of small molecule compounds (compounds having molecular weight of about 1000 or less) has been possible by joining various types of chromatography and a detector. For example, in metabolomics research that is omics science based on all metabolites in a living body, complex phenotypes in microorganisms, plants, animals, or food samples can be analyzed quantitatively with high resolution. For this reason, the exhaustive quantitative analysis does not only contribute to basic science research, but has also started to be used as a powerful analysis tool in practical industrial research such as support for drug development, toxicity evaluation, and food function analysis. Moreover, the exhaustive quantitative analysis has been essential technology in the field of pesticide residue tests or drug residue tests.
Generally, since small molecule compounds have diverse physicochemical properties, various kinds of separation technology are necessary for comprehensive measurement of such compounds.
In SFC, a supercritical fluid is used for the mobile phase (see JP 2006-52968 A). The supercritical fluid is a substance in a state above a critical temperature and a critical pressure, and has nature favorable for chromatography such as low viscosity and high diffusivity. SFC maintains high separation ability even in high flow velocity analysis, and has a potential of being capable of selecting a wide range of separation modes by adding a polar solvent (modifier) or by changing a temperature or a back pressure. Carbon dioxide, which is generally used in SFC, has a critical pressure of 7.38 MPa and a critical temperature of 31.1° C. that is relatively close to normal temperature, is non-flammable and chemically unreactive, and very pure carbon dioxide is available at a low cost. For this reason, carbon dioxide is most often used in SFC. Supercritical carbon dioxide (SCCO2) has a physical property of low polarity close to hexane, and the polarity of the mobile phase can be changed significantly by adding a polar organic solvent such as methanol as a modifier. Accordingly, heretofore, SFC has been applied as a separation analysis technique useful for fast separation analysis of lipids that represent hydrophobic metabolites.
On the other hand, liquid chromatography (LC) is commonly used for analysis of metabolites, and it can be said that LC is the most widely used chromatography method. However, LC has different measurement conditions depending on measurement targets, and cannot simultaneously separate a wide range of metabolites by one liquid chromatograph.